As an attempt to increase fuel-efficiency of automobiles, electric power assisted steering systems have been introduced to the automotive market. These systems assist in steering vehicles by applying additional torque to the steering system whenever torque is sensed in the steering shaft. Although these systems have increased feul-efficency, they are unable to differentiate between torque created by forces at the steering input and at the steering output. Forces originating at the steering output may be the result of the road wheel coming into contact with a curb or a large bump in the road, while forces originating at the steering input are those forces that a driver applies. Because the currently exsisting systems are unable to differentiate between these forces, the forces originating at the steering output (e.g. a road wheel) are sensed as an input torque and cause the system to apply additional torque to the steering shaft in the same direction, thereby causing vibration in the steering input (e.g. a steering wheel) and decreasing stability of the system.
While it is important to reduce the effort drivers must use to steer a vehicle, it is of equal importance to resist forces that originate at the steering output. Forces originating at the steering output sometimes steer the vehicle in an unintended direction and applying additional torque to the steering shaft may exacerbate this problem. For these reasons, there is a need in the automotive art, if not other arts, for a power assisted steering system that is able to distinguish between forces originating at the steering input and the steering output and to react to these forces differently.